I guess I take the middle road here. I have two .45-70's. My first was part of the intial run Marlin made in 1972. Straight grip and a microgroove barrel. The other is a Number 1 purchased in 1978. I have taken deer and hogs with both. There is no doubt that at the short ranges I used them they were wickedly effective. I have even taken a few woodchucks with the Number 1 -- a few at around 200 yards.I am sure that if you knew where to hold and practiced a bit you could stretch the ranges considerably. Neither of my rifles are set up for long range shooting; I just sight them in a little high at 100 yards and I am pretty much on the money at 150 or a little less. At woods ranges that is fine. A few years ago I spent an afternoon battering a 300 yard plate with a trapdoor Springlield.You could wind your watch and cash your paycheck waiting for the sound of those bullets impacting the target. A 500 grain bullet makes quite a fuss when it arrives on scene.
That said, even though they will toss a bullet one hell of a long way with amazing accuracy, I don't consider the cartridge a long range affair. No question that it can be done. And if it is your thing then be my guest. I am all for it, although it strikes me a slightly incongruous to crank up a ladder sight on a nineteenth century rifle to hit something you have lasered with a twenty-first century rangefinder. Hey, but if that's your thing....